The first spectroscopic and photometric solutions of the eclipsing binary, V335 Ser Z. Bozkurt Ege University, Faculty of Science, Dept. of Astronomy and Space Sciences, 35100 Bornova, _ Izmir, Turkey article info Article history: Received 14 February 2011 Received in revised form 9 March 2011 Accepted 16 March 2011 Available online 22 March 2011 Communicated by P.S. Conti Keywords: Stars: binaries Eclipsing — stars: fundamental parameters Individual — stars: V335 Ser abstract We present the first analyses of the radial velocity and BV light curves for the eclipsing binary system, V335 Ser. This double-lined eclipsing binary has an eccentricity of 0.14. BV photometric light curves and double-lined radial velocities were solved simultaneously using an improved version of the Wilson–Devinney computer program. The masses and radii of the component stars were obtained as M 1 = 2.02 ± 0.01 M  , M 2 = 1.84 ± 0.02 M  , R 1 = 2.03 ± 0.02 R  and R 2 = 1.60 ± 0.01 R  . We estimated the semi-amplitudes of the radial velocity curves of the primary and secondary components as K 1 = 106.31 ± 0.88 km s 1 and K 2 = 116.94 ± 0.88 km s 1 , respectively. As determined by absolute visual magnitude and corrections for interstellar extinction, the distance of the system from earth was found to be d = 219 ± 24 pc. The existence of apsidal motion is presented as means of eclipse time, and the apsi- dal motion rate was found to be _ x obs ¼ 0:01302  0:02563 deg cycle 1 . The corresponding apsidal motion period was found to be U = 261 ± 514 years. Using the absolute properties and apsidal motion parameters obtained from period analysis, we computed the observational and theoretical internal struc- ture constants to be logk 2,obs = 1.53 and logk 2,theo = 2.44, respectively. We also present the evolutionary status of the component stars in an H-R diagram using solar metallicity and four helium content values. Both component stars are slightly evolved from the ZAMS. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction The photometric variation of V335 Ser (HD143213; SAO121294; GSC 353-301; P =3 d .45, V max =7 m .47, Sp.A0) was found using the TYCHO instrument of the Hipparcos satellite (Makarov et al., 1994). Bastian and Born (1997) classified V335 Ser as an Algol type binary system with a period of 3.4500 ± 0.0003 days. This classification was determined using Born’s visual observations, which were made between June 1996 and August 1997. According to the visual light curve, the secondary minimum is located at phase 0.545 ± 0.006, and the phase shift of 0.5 was attributed to the eccentricity of the orbit. The authors gave an ephemeris for primary minima as HJDMinI ¼ 2 450 304:35ð2Þþ 4:4500ð3Þ E: ð1Þ Taking this into account, the author’s redrew the TYCHO light curve, which has a secondary minimum at phase 0.550 ± 0.007. Bastian and Born (1998) improved the ephemeris of primary minima by applying a least-squares fit to all available eclipse timings as HJDMinI ¼ 2 450 304:357ð11Þþ 4:449896ð62Þ E: ð2Þ The authors also made an independent fit to the timings of second- ary minima and found a period of 3.449820 (±0.000048) days, with a mean phase of 0.541 ± 0.006. They emphasized that this value is a highly significantly offset from phase 0.5. In this study, we aimed to simultaneously obtain BV photoelec- tric light curves and radial velocity curves solutions of V335 Ser, thus deriving the first estimates of the absolute properties of the system. 2. Observations 2.1. Photometric observations Photometric observations of the system were carried out at Ege University Observatory Research and Application Centre with a 48-cm Cassegrain telescope equipped with a high-speed, three-channel photometer. Observations were made in B and V bandpasses. The coordinates, magnitudes in V and colour indices of V335 Ser and comparison stars are listed in Table 1. The system was observed on 22 nights between May 2006 and July 2010. BV light curves were obtained during the 2006–2007 observation seasons. Later observations were made to transform the magnitudes to the standard UBV system and to obtain new times of minimum. We used HD 142981 and HD 143110 as comparison stars and, based on measurements of these stars, calculated the atmospheric extinction coefficients in each colour for each observation night. We then corrected all instrumental differential magnitudes in terms of the variable star minus the 1384-1076/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.newast.2011.03.007 E-mail address: zeynep.bozkurt@ege.edu.tr New Astronomy 16 (2011) 412–419 Contents lists available at ScienceDirect New Astronomy journal homepage: www.elsevier.com/locate/newast